Tachometer carb tuning advices needed

[KostasVolos]

Ok,here's the situation.
We have six brand new Stihl MS180 2-mix
chainsaws which we are
going to use while making a wildfire protection zone around
an olive oil extraction facility.
All of them have adjustable carburetors fitted,MM and
their ( oval shaped )intake inserts are drilled open .

The crew consists of eight persons.And every each one of us
has it's own theory about tuning the carburetors firstly with a tach
and then maybe trim a bit with ear.
So ,-what a fantastic idea indeed!-I'm asking for some help from the crowd.

The MS180 has an official idle value of 2800 rpm.Max power at
10,000 rpm and max rpm is 14,000.

In the manual it is stated that it can be fitted with 12",14" & 16" 3/8"lp 0.43 bar (narrow kerf )and chain combo ,
as also with 3/8"lp 0.50 (standard kerf) of the same lengths.

So first series of questions :
This 14,000 max rpm figure applies with bar and chain on ?
If yes which of the
aforementioned six combos ?
Based on what documentation ?

Adjusting max rpm ( H ) without
bar and chain ( is this not the real " no load " situation ,after all ? ) is
out of question ?

My own personal take on the matter is to just turn in the H until
the value on the tach still oscillates ( visual indication of "four stroking ") while getting close to 13,500 rpm or so,
but not as high as 14,000 rpm.
All done with the bar and chain combo that the chainsaw is going
to be used with.

But there are voices in the crew that insist at the "only " and "real"
no load situation ,this being without bar and chain .
Meaning to tune the chainsaw without 'em .

Sounds logical ,since "we are talking about a small engine and not a chainsaw.The same engine could power other tools and machinery .
Which then would have been the no load situation ,at each case ? "
I'm confused by now ...

 

[Vintage Engine Repairs]

The correct way is to fit the intended bar and chain, ensure its correctly tensioned, clean AF, full tank of fuel and tune in the cut.
I don’t run my equipment on the ragged edge, I want them to be 4 stroking until they are under good load. Also, run a good oil at either 32:1 or 40:1. Good doesn’t necessarily mean synthetic, but just don’t get the cheapest store brand. Stick with name brands.

Edit:

This may help

 

[Vintage Engine Repairs]

Sorry I have just edited my above post, as i’ve remembered that you’ve done a MM and opened the ports.

Because you’ve changed the parameters that were used to get to the 14k max rpm it’s a better idea not to rely on manual specs.

Get it under load and tune by ear.

 

[ericm979]

Get a copy of the Stihl shop manual for that saw. They have a well described and easy to follow tuning procedure in it. I've used it for a couple Stihls and it results in a good safe tune.
There's a manuals section on this web site.

 

[KostasVolos]

Get a copy of the Stihl shop manual for that saw. They have a well described and easy to follow tuning procedure in it. I've used it for a couple Stihls and it results in a good safe tune.
There's a manuals section on this web site.

I already have the service and repair manual and on page 36 is described how to adjust the idle
LA (air cut off) on the stock Zama fixed-jet carburetor .
These chainsaws are custom fitted with fully adjustable carburetors ( Walbro WT-215-1 clones ).
The original Zama carb that the Stihl MS170 & MS180 come with is a piece of junk .

 

[ballisticdoughnut]

Tune them for best performance in the cut, just don’t exceed 14k rpm.

 

[ZeroJunk]

Well, the only stock carburetor here anyway has a fixed high speed jet and the only adjustment is the low idle speed.
If you have a fully adjustable carb I would set the high speed at 13,000 with the bar and chain you intend to use.
Turning it up to 14,000 will gain you nothing that you will ever notice and cause you problems if you run in to bad gas or get an oil ratio off a little.

 

[Defdice]

Tuning needs to be done with the bar and chain - which ever bar and chain that will be used. I had a MS251 and the manual lists the max rpm as "Maximum permissable engine speed with cutting attachment: 13,000 rpm". The MS180 manual seems less detailed. Your own personal take is correct, and @ZeroJunk advice is great too. Just be sure to do the tuning after the saws are quite warmed up.

 

[KostasVolos]

Well ,today I tried to tune two of those MS180.

Started with both H & L one turn out of lightly seated and with two turns in the idle screw from pin touching the throttle lever.

Let the chainsaw warm for couple of minutes and then adjusted the L for max revs between stall points .
Pressed full throttle,saw did not accelerate but bogged and died.
Had to turn out the L ( richer ) almost a turn to have the chainsaw accelerate without bogging.Now idle screw is almost touching the throttle lever to have the 2700 rpm figure on the tach.

H adjustment needed a bit of turn in to increase up to 12.500 rpm WOT,from around 9000 rpm initially.
Let it at 12.700 ,but can't hear any four stroking but rather ...a gentle scream -shall I say .In the cut the
saw behaves superb and while burying the 16" bar on chinese chestnut recently fallen logs ( about 20" dia. ) the sound cleans up pretty nice,without the chainsaw to bog ,
but instead it's cutting like a champ!

Both of them had the same behaviour regarding the L adjustment.Far richer than the "highest revving midpoint between stalling rich and stalling lean ".
It seems that the saw needs plenty of gas to accelerate properly from idle to WOT.

Is it because of the 2-mix engine?
Or from the much more free-flowing air intake than the stock one?

Not quite sure.
Any ideas ?

 

[huskihl]

Well ,today I tried to tune two of those MS180.

Started with both H & L one turn out of lightly seated and with two turns in the idle screw from pin touching the throttle lever.

Let the chainsaw warm for couple of minutes and then adjusted the L for max revs between stall points .
Pressed full throttle,saw did not accelerate but bogged and died.
Had to turn out the L ( richer ) almost a turn to have the chainsaw accelerate without bogging.Now idle screw is almost touching the throttle lever to have the 2700 rpm figure on the tach.

H adjustment needed a bit of turn in to increase up to 12.500 rpm WOT,from around 9000 rpm initially.
Let it at 12.700 ,but can't hear any four stroking but rather ...a gentle scream -shall I say .In the cut the
saw behaves superb and while burying the 16" bar on chinese chestnut recently fallen logs ( about 20" dia. ) the sound cleans up pretty nice,without the chainsaw to bog ,
but instead it's cutting like a champ!

Both of them had the same behaviour regarding the L adjustment.Far richer than the "highest revving midpoint between stalling rich and stalling lean ".
It seems that the saw needs plenty of gas to accelerate properly from idle to WOT.

Is it because of the 2-mix engine?
Or from the much more free-flowing air intake than the stock one?

Not quite sure.
Any ideas ?

Each carb and each saw are unique. Set the L where you’re happy, then the h. And then back to the L so that it idles and accelerates smoothly.

 

[KostasVolos]

Well,I 've noticed that all of those
WT-215 clones installed lack the
"acceleration pump" thingy .
They do not have the brass plug near the throttle shaft ,where under it resides the acceleration pump piston and spring.
Haven't dismantled the throttle shaft to actually check if an accelerator pump is present ,but since there isn't any brass plug ,how on earth would be possible to actually have an accelerator pump present ?

So,without an accelerator pump the idle needle adjustment ( L ) has to be adjusted to the rich side,in order for the chainsaw to accelerate smoothly and without hesitation from idle to WOT.
Correct ?

 

[adedeluca]

Ok,here's the situation.
We have six brand new Stihl MS180 2-mix
chainsaws which we are
going to use while making a wildfire protection zone around
an olive oil extraction facility.
All of them have adjustable carburetors fitted,MM and
their ( oval shaped )intake inserts are drilled open .

The crew consists of eight persons.And every each one of us
has it's own theory about tuning the carburetors firstly with a tach
and then maybe trim a bit with ear.
So ,-what a fantastic idea indeed!-I'm asking for some help from the crowd.

The MS180 has an official idle value of 2800 rpm.Max power at
10,000 rpm and max rpm is 14,000.

In the manual it is stated that it can be fitted with 12",14" & 16" 3/8"lp 0.43 bar (narrow kerf )and chain combo ,
as also with 3/8"lp 0.50 (standard kerf) of the same lengths.

So first series of questions :
This 14,000 max rpm figure applies with bar and chain on ?
If yes which of the
aforementioned six combos ?
Based on what documentation ?

Adjusting max rpm ( H ) without
bar and chain ( is this not the real " no load " situation ,after all ? ) is
out of question ?

My own personal take on the matter is to just turn in the H until
the value on the tach still oscillates ( visual indication of "four stroking ") while getting close to 13,500 rpm or so,
but not as high as 14,000 rpm.
All done with the bar and chain combo that the chainsaw is going
to be used with.

But there are voices in the crew that insist at the "only " and "real"
no load situation ,this being without bar and chain .
Meaning to tune the chainsaw without 'em .

Sounds logical ,since "we are talking about a small engine and not a chainsaw.The same engine could power other tools and machinery .
Which then would have been the no load situation ,at each case ? "
I'm confused by now ...

Rpm in the WOOD is what matters. We are cutting under load. Did You watch Bucking Billy Ray he wil guide you He is a woodsma and a tree faller

Enjoy. God Bless

 

[increasing]

The correct way is to fit the intended bar and chain, ensure its correctly tensioned, clean AF, full tank of fuel and tune in the cut.
I don’t run my equipment on the ragged edge, I want them to be 4 stroking until they are under good load. Also, run a good oil at either 32:1 or 40:1. Good doesn’t necessarily mean synthetic, but just don’t get the cheapest store brand. Stick with name brands.

Edit:

This may help

Very well illustrated video

 

[singinwoodwackr]

Get a copy of the Stihl shop manual for that saw. They have a well described and easy to follow tuning procedure in it. I've used it for a couple Stihls and it results in a good safe tune.
There's a manuals section on this web site.

These are modded saws